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Anechoic Chamber RF Testing for Electromagnetic Compliance

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • Anechoic chamber RF testing is an indoor RF measurement and testing method.

  • For RF testing, an isolated room free of electromagnetic signals is required and anechoic chambers serve this purpose.

  • Anechoic chamber RF testing is most commonly used for measuring antenna patterns and characterizing the performance of antennas.

Anechoic chamber

Anechoic chamber RF testing is conducted for the verification of radiated emissions limits

For any product to reach the market, it must first be confirmed that the product is electromagnetically compliant. Electromagnetic compliance increases customer trust in products and ensures reliability and safety. To ensure this, electromagnetic compatibility (EMC) testing is a common procedure in the electronics industry to ensure products meet EMC standards.

EMC testing verifies whether a device satisfies the acceptable frequency range for which it is designed. EMC testing is conducted at every stage of product development to identify the source of EMI. EMC testing validates that the emissions from electronic equipment meet the limits set by regulatory bodies such as CISPR, IEC, and IEEE. Anechoic chamber RF testing is one such test that is conducted for the verification of radiated emissions limits. 

Radiated Emissions and Limits

Today, most electronic devices use electromagnetic fields or electromagnetic signals to operate. However, devices are vulnerable to external electromagnetic fields and emissions, which can hamper their normal functioning. These electronic devices are also capable of emitting electromagnetic signals that disturb the workings of nearby equipment. Such emissions in the frequency range of 30 MHz and 1 GHz are called radiated electromagnetic interference or radiated EMI. 

Radiated emissions from electronic devices can hinder their safety. To control radiated emissions from each category of devices, there are regulatory bodies that set emissions limits. It is not advisable to continue using a device if the emissions exceed the limits set by these regulatory agencies (including CISPR, IEEE, or IEC). The use of such devices can lead to serious issues.

To prevent the harmful effects of emissions, it is important to take the necessary precautions and use proper mitigation methods. To accomplish this, manufacturers conduct EMC testing to address all potential EMI sources in a product. 

EMC Testing 

At every stage of product development, EMC testing is conducted to identify EMI sources and ensure that electromagnetic compliance has been achieved by the time of final assembly. 

What Does EMC Testing Do?

EMC testing validates the electronic equipment's ability to function normally without affecting the operation of external devices in the vicinity. This is identified by the measurement of the electromagnetic disturbances introduced by them into the external space. EMC testing measures the radiated emissions from the electronic device and then compares them to the limits stated in the EMC standards. If a device fails to adhere to the standards, the design is not electromagnetically compliant. 

When Is EMC Testing Used?

EMC testing is used for finding sources of EMI that emit unacceptable amounts of radiated emissions. Products go through multiple rounds of EMC testing, and this cycle continues until the final assembly stage and until the emissions are within permissible limits. EMC testing is used for troubleshooting EMI-related issues associated with existing products as well.

EMC testing applies to any system such as computers, power cables, antennas, or home appliances. For an estimation of the radiated EMI from a device (source of EMI), measurement setups are made for EMC testing or RF testing.

Commonly employed RF testing setups are:

  • Open area test sites (OATS) 

  • GigaHertz transverse electromagnetic (GTEM) 

  • Reverberation chambers (RC)

  • Anechoic chambers

Let’s discuss anechoic chamber RF testing.

Anechoic Chamber RF Testing

Anechoic chamber RF testing is an indoor RF measurement and testing method. For RF testing, an isolated room free of electromagnetic signals is required, and an anechoic chamber serves this purpose. 

Anechoic Chambers

Anechoic chambers are screened rooms fully or partially covered with electromagnetic absorbers. They create an enclosure with high shielding attenuation against electromagnetic interference. An anechoic chamber absorbs 100% of ambient emissions but reflects the minimum amount of internal radiation.

The Test Set-Up

Properly setting up anechoic chamber testing scenarios is crucial for conducting error-free RF testing and measurements. In a well-constructed anechoic chamber, the electronic device under test receives RF signals from a signal source. Since the chamber does not internally reflect transmitted RF waves, any electromagnetic signal measured from the test site corresponds to radiated emissions from the device under test. If the radiated emissions measured are within the acceptable limits given (as per the standards applicable to the device category under test), then it ensures the integrity of the product.

Anechoic chamber RF testing is most commonly used for measuring antenna patterns and characterizing the performance of antennas. RF testing in an anechoic chamber also allows radar cross-section and radar scattering over a wide frequency range. Depending on the type of system, test, and measurements, anechoic chamber settings are established as tapered, millimeter-wave, compact range, small near-field scanner, and large near-field scanner chambers. 

Cadence software can assist you in modeling an anechoic chamber in the finite difference time domain for electromagnetic compliance of the electronic product over a wide frequency range.  Subscribe to our newsletter for the latest updates. If you’re looking to learn more about how Cadence has the solution for you, talk to our team of experts.